1. Field of the Invention
The present invention relates generally to a power conversion system, and more particularly to an innovative one which is applied to hybrid electric vehicle (HEV).
2. Description of Related Art
Owing to the restrictions of traffic lights and traffic jam, about 30% energy of the electric engines is converted to heat and drained into the environment in case of braking; however, storage of wasted energy is critical with the growing energy cost and demanding calls for environmental protection; HEV allows to recycle the braking energy by an additional energy storage system, and drive the internal combustion engine when climbing or acceleration.
HEV (Hybrid Electric Vehicle) is operated by driving the wheels with its engine and electric motor. Generally, the vehicle is equipped with driving batteries as the power conversion of electric motor, and the driving batteries are recharged by the generator, which is driven by the engine, or used as braking regenerator driven by inertia during braking. The advantages of HEV lie in that, when the vehicle is started or stopped, the motor is not activated under the driving of generator, if a certain speed is not reached. Thus, the motor is always kept in optimum working conditions with good dynamic property and lower emissions, and used as the source of electric energy. It can be operated only by refueling.
For the power conversion required for HEVs, the currently available LFP batteries are implemented in series to meet the voltage required for HEVs; yet there are three common problems: one: LFP batteries have a very high cost, e.g.: over 100 batteries are required for existing 320V system; two: recharging time of LFP batteries is very long; three: complex assembly and numerous connections cause the hazards of risk, poor reliability and difficulty in quality control.
As a whole, it is very necessary to improve existing technologies to address the aforementioned problems of prior art, such as: extremely huge amount of batteries, longer recharging time, complex assembly and hazards of risk caused by numerous connections.